At daylight on Sunday, the 16th, Gen. Buckner, (whose two superior officers, Floyd and Pillow, had run away,) sent a flag of truce asking for commissioners to consider terms of capitulation. Grant replied by the bearer, in a letter, two of whose phrases have become permanent contributions to the proverbial part of the English language: "Yours of this date, proposing an armistice, and appointment of commissioners to settle terms of capitulation, is just received. No terms other than unconditional and immediate surrender can be accepted. I propose to move immediately upon your works." Buckner's reply was in a very disgusted tone, and it may be excused to him under the circumstances, that he used some very curious explanatory phrases, and that he called names. But he came down, though it was from an extremely high horse, rejoining: "The distribution of the forces under my command, incident to an unexpected change of commanders, and the overwhelming force under your command, compel me, notwithstanding the brilliant success of the confederate arms yesterday, to accept the ungenerous and unchivalrous terms which you propose." The correctness of Grant's estimate of this whole movement was well proved by its instantaneous result--the evacuation of Columbus at one end of the rebel line, and of Bowling Green in the middle, and the falling back of the whole rebellion down to the southern boundary of Tennessee. The first great victory since Bull Run, the first important campaign in the West, it encouraged and elevated the spirits of the whole North, and in equal measure it alarmed and enfeebled the South. It had flung back the rebellion two hundred miles, along the whole length of Kentucky, across that State and Tennessee. With soldierly promptitude and energy, Grant followed up his victory by pushing the enemy, according to the Napoleonic maxim, that "victory is, to march ten leagues, beat the enemy, and pursue him ten leagues more." Immediately after Donelson, Grant was made major general of volunteers by commission dated on the day of the fall of the fort, and was placed in command of the "Military District of West Tennessee," consisting of a long triangle with its northern point at Cairo, its base at the south, on the Mississippi State line, and its sides the Tennessee and Mississippi rivers. Thus promoted, Grant had already pushed southward. Foote's gunboats ascended the Cumberland, the troops kept abreast of them; Clarksville, with twenty days' subsistence for Grant's whole army, was occupied on Feb. 20th, four days after the capture of Donelson; and on the 23d, the advance of Buell's army, operating in conjunction with Grant's, entered Nashville.